The present invention relates to a thermal transfer printing method and, in particular, to an indirect thermal transfer printing method.
An indirect thermal transfer printing method of the conventional type is an image formation method wherein a device such as shown in FIG. 1 is used. In FIG. 1, numeral 10 denotes a rotatable intermediate transfer drum of which the surface is formed of an elastic material of good releasing property such as silicone rubber, fluorine-containing rubber or the like. Numeral 11 denotes a recording part which is arranged so that a thermal transfer ink sheet 12 can be pressed against the intermediate transfer drum 10 with a thermal head 13. In printing, the ink sheet 12 is moved in the direction indicated by an arrow as the intermediate transfer drum 10 rotates. Numeral 14 denotes a transfer part which is arranged so that an image receptor 15 can be pressed against the intermediate transfer drum 10 with a pressing roller 16. In transferring, the image receptor 15 is moved in the direction indicated by an arrow.
The thermal head 13 heats the thermal transfer ink sheet 12 so as to selectively soften or melt portions of the ink thereof, which is transferred onto the surface of the intermediate drum 10. While the intermediate drum 10 and the ink sheet 12 are thus moved in the directions indicated by the arrows, respectively, the softened or melted ink is transferred onto the intermediate drum 10 thereby forming an ink image 17 thereon. As the drum 10 rotates, the ink image 17 is moved to the transfer part 14, pressed against the image receptor 15 there, and transferred onto the image receptor 15 to form a final ink image 18 thereon.
According to such an indirect thermal transfer printing method, the ink of the ink sheet which is heated with the thermal head 13 is transferred onto a smooth surface of the intermediate transfer drum 10. Hence, there has been overcome such a problem involved in a common thermal transfer method that unclear transferred images are likely to be formed on a recording sheet of which the surface is poor in smoothness. Further, according to the indirect thermal transfer printing method of the conventional type, ink images on the intermediate transfer drum 10 are transferred onto the image receptor 15 by pressing thereagainst under a relatively large pressure with the pressing roller 16. Hence, the quality of the thus obtained images is not subject so much to the superficial conditions of the image receptor. Therefore, the indirect thermal transfer printing method provides clear images regardless of the type of the image receptor 15.
With this type of indirect thermal transfer printing method, however, there are problems left unsolved such as high cost for consumable items due to a large amount of expensive ink sheet consumed in thermal transfer printing and low printing speed.
It is an object of the present invention to provide an indirect thermal transfer printing method which is capable of effectively utilizing a thermal transfer ink of an ink sheet while improving the printing speed.
This and other objects of the invention will become apparent from the description hereinafter.